1. Field of the Invention
The present invention relates to new bisphosphonic acid derivatives as represented by the following formula (I') or pharmaceutically acceptable salts thereof. ##STR2## in which
R.sup.1 represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, a cycloalkyl group having from 3 to 10 carbon atoms, a phenyl group, an alkenyl group having from 2 to 10 carbon atoms which may be substituted by a phenyl group or a phenyl substituted alkyl group having from 1 to 5 carbon atoms which may be substituted by an alkoxy group having from 1 to 5 carbon atoms;
R.sup.2 represents a hydrogen atom or an alkanoyl group having from 2 to 6 carbon atoms;
R.sup.3, R.sup.4, R.sup.5 and R.sup.6 may be the same or different, each represents a hydrogen atom or an alkyl group having from 1 to 5 carbon atoms; provided that when R.sup.1 represents a methyl group, an ethyl group, an isopropyl group or a tert-butyl group, at least one of R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 represents a substituent other than hydrogen atom.
The present invention also relates to a bone resorption-inhibitor and an anti-arthritis containing, as an active ingredient, a bisphosphonic acid derivative as represented by the following formula (I) or a pharmaceutically acceptable salt thereof. ##STR3## in which
R.sup.1 represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, a cycloalkyl group having from 3 to 10 carbon atoms, a phenyl group, an alkenyl group having from 2 to 10 carbon atoms which may be substituted by a phenyl group or a phenyl substituted alkyl group having from 1 to 5 carbon atoms which may be substituted by an alkoxy group having from 1 to 5 carbon atoms;
R.sup.2 represents a hydrogen atom or an alkanoyl group having from 2 to 6 carbon atoms;
R.sup.3, R.sup.4, R.sup.5 and R.sup.6 may be the same or different, each represents a hydrogen atom or an alkyl group having from 1 to 5 carbon atoms.